This is NOT a knock on BL, he's a fine coaching talent, and although he's not my first choice, I would have no problem with him as Bears HC.
That being said, It's an absurd notion that Tom Brady was developed by Byron Leftwitch. He was fully formed when he arrived at Tampa Bay, already an unquestioned first ballot Hall of Fame inductee. The Bucs were looking like a joke with Brady until the QB asserted himself. The pieces of offense, that were combined with BL's--and put Tampa Bay over the top--were from Brady and his years at NE.
Tom Brady developed Byron Leftwitch, whose offense now features plays and concepts he learned from arguably the greatest QB that's ever played the game. Tom Brady, sure, probably learned a thing or two from BL.